This invention relates to a document transport belt, and more particularly to a document transport belt suitable for use in an automatic document handler in an electrostatographic copying machine.
Frequently, it is necessary to feed single sheets of paper from a stack in rapid sequence, for example, in order to more fully utilize the high speed copying capabilities of modern reproduction or copying machines, it is desirable to employ an automatic document handler for placing original documents to be copied on the platen of the reproduction machine, and to remove them from the platen after the copying process, to minimize delays associated with manual steps carried out by operators. To accomplish this function, the automatic document handler must first separate the document to be copied from others awaiting copying. Then, the separated document is forwarded to the machine platen, properly located or registered thereon, copied and removed from the platen to enable succeeding copies to be placed on the platen.
In such a process, the document to be copied must be rapidly separated from the stack of documents in the document supply tray; multiple fed documents must be separated from the desired document and returned to the document tray; the single document must be forwarded to the platen and registered thereon; and after copying, removed therefrom. This entire process must be accomplished rapidly to remove the copied document to place the succeeding document on the platen preferably between copy cycles of the machine. In high speed machines capable of producing more than one copy a second, it is difficult to carry out the entire document handling process between copy cycles. However, an automatic document handler should be able to accomplish the steps of removing one document and placement of a succeeding document on the platen in less than one second. At such a speed, rapid acceleration and positive feeding of the document is imperative. Nevertheless, the document handler must also be designed to produce minimal wear and tear on the documents, prevent misfeeds or multifeeds, and minimize jams to prevent damage to the documents which may be irreplaceable.
In addition to the requirements associated with the rapid positioning of a document and its subsequent removal from the platen, a document feed belt in an automatic document handler, frequently provides the background or framework for the document to be copied. Generally, at least a portion of the document feed belt overlays the platen and thus forms the backdrop for the document being copied. Accordingly, it is desirable that the document feed belt be white or as nearly white as possible. However, conventional materials which may be used for the document feed belt, such as conventional rubbers, tend to undergo mechanical degradation resulting from mechanical stress due to high speeds of operation. Moreover, many conventional materials are easily degraded by oxidation at elevated operating temperatures. Degradation by oxidation is particularly pronounced in high speed modern copying machines in which ozone is generated by corona charging devices operating at high capacities. The mechanical and chemical degradation of document feed belts are frequently visible in such characteristics as surface cracking, tackiness of the surface, and dirt pickup or discoloration of the initially white document feed belt.
A further problem associated with prior art document feed belts made of such materials as conventional rubbers resides in the fact that such prior materials tend to be relatively easily abraded and hence, has relatively short life.
In U.S. Pat. No. 3,482,676, there is disclosed a document feed belt which is made of two layers, an inner layer of flexible electrically conductive material such as graphite impregnated rubber, and an outer layer of a flexible light reflective materials such as white neoprene. The inner layer of electrically conductive material will assist in the dissipation of undesired static electrical charge on the belt while the white outer layer will provide a clean background for the document being copied.
U.S. Pat. Nos. 3,829,082, 3,889,943 and 3,941,376, all disclose automatic document handlers which utilize platen transport belt or document feed belt. For construction of such belts, all three of these patents refer to the belt construction disclosed in said patent 3,482,676.
In U.S. Pat. No. 3,889,942, there is disclosed a device for facilitating the feeding of documents into a reproduction machine, which includes a curved entry sheet or strip for holding the sheets in aligned position and for flatening curls or undulations in the sheets. The curled strip is made of a transparent plastic or Mylar.
In U.S. Pat. No. 3,931,090, there is disclosed a highly reversion resistant polyisoprene elastomer composition vulcanized with a low sulfur content for use in paper feed belts. The low sulfur vulcanizate of isoprene provides high resistance to physical degradation due to dynamic mechanical stress under operating conditions.
Finally, in U.S. Pat. No. 4,023,791, there is disclosed a semi-automatic document feeder for use with a photocopying machine, in which a plurality of drive belts form a conveyor loop. The belts of this patent are made of cloth-based neoprene or of cloth-based synthetic rubber.
Although the document feed belts of the prior art have provided satisfactory service, there is a need for improved document feed belts which have stable and controllable coefficient of friction for dependable feeding of documents, high resistance to ozone attack, whiteness stability to provide a clean background for the document to be copied, superior mechanical properties including resistance to abrasion, surface cracking, and dirt pickup.
It is, therefore, an object of the present invention to provide an improved document feed belt for use in automatic document handlers.
It is another object of the present invention to provide an improved document handling apparatus in which the document feed belt has improved mechanical stability, improved resistance to ozone attack, and improved whiteness stability.
These and other objects of the invention will be apparent from the following disclosure.